1. Field of the Invention
The present invention relates generally to a web transporting method and apparatus, and more particularly to a web transporting method and apparatus that transports a web while floating the web by jetting air to the web.
2. Description of Related Art
Various types of apparatuses that transport webs while floating the webs by jetting air to the webs are disclosed in Japanese Patent Provisional Publication Nos. 60-93056, 61-203055, 62-167162, 63-225058, 2-163252 and 8-245028.
These apparatuses transport the webs without coming into contact with the webs. For example, in the apparatus disclosed in Japanese Patent Provisional Publication No. 60-93056, a number of air jets are formed in an arc-shaped transporting surface changing a running direction of a web, and the web is transported while compressed air is jetted from the air jets to float the web. The apparatus has guide plates, which are continuous to the transporting surface at an entrance and an exit of the transporting surface, to unify the pressure of the air jetted from the air jets. The apparatus disclosed in Japanese Patent Provisional Publication No. 61-203055 has blocks that block air jetted from air jets at an entrance and an exit of a transporting surface. The apparatus disclosed in Japanese Patent Provisional Publication No. 62-167162 has straightening vanes that straightens air jetted from air jets at an entrance and an exit of a transporting surface. The apparatus disclosed in Japanese Patent Provisional Publication No. 63-225058 has transporting plates at both ends of a transporting surface. In the apparatus disclosed in Japanese Patent Provisional Publication No. 2-163252, a number of slits are formed widthwise in a transporting surface to unify the pressure of air jetted from air jets. The apparatus disclosed in Japanese Patent Provisional Publication No. 8-245028 supports a web while bending the web.
However, in these apparatuses transporting the webs without coming into contact with the webs, the air pressures and the transporting tensions of the webs easily change, and the floating amounts of the webs easily change. As a result, the webs have twistings, biases and speed unevenness, and the webs come in contact with the transporting surfaces, which causes them to be damaged. Also, these apparatuses can not be used before or after precise coating process.
In view of the foregoing, it is an object of the present invention to provide a web transporting method and apparatus which reduces a twisting and a bias of a web to stably transport the web.
To achieve the above-mentioned object, the present invention is directed to a web transporting method, wherein: a web is transported while being floated by air jetted from at least one of a jetting hole and a jetting slit, the at least one of the jetting hole and the jetting slit being formed in a transporting surface; and edges of the web are supported by edge rollers.
According to the present invention, the web is transported while the edges of the web are supported by the edge rollers. Thus, the floating amount of the web can be kept, and the supplied air can be prevented from escaping from the space between the transporting surface and the web through the edges of the web. Therefore, the web can be stably floated and transported with little air.